On Sun, 30 Jul 2017 17:18:11 +0200, Robert Roland
wrote:

On Sun, 30 Jul 2017 11:54:52 +0100, T i m wrote:

Well, whilst I think they are 'quite clever' I agree that it probably
couldn't test the TOP223Y's.

http://www.eetimes.com/author.asp?se...doc_id=1329331

I have one similar. Yes, they are impressively clever for the money.

Aren't they. ;-)

By they do not do ICs, only generic components.

My only thought was that whist the TOP is actually a 'clever' 3 pin
device, there may be some basic logic that it could respond to that
might make the tester think it was a working FET or Triac or some
such? eg. You might be able to use it as a go / no-go test, *if* it
detected something positive (however misdirected) in comparison to a
good one?

The only component
that I found will fool it, was a germanium power transistor. The low
Vbe, combined with the low DC gain probably threw it off.

Ok ... and that's not even a 'clever' component at such. eh. ;-)

On that ... do you think it might be worth testing (or even just
replacing) the two main caps in case they are getting weak?

Hard to say. There are so many factors that affect the aging of caps.
It does not take many seconds to take them out and test them, though.

True, as whatever 'glue' they used to hold stuff down seems to have
gone off a bit in any case. Maybe I'll replace the diodes first and if
the unit then works, treat it to a fair of quality (low ESR?) caps at
that point.

I note
they have an extra heat shrink 'skin', probably because they are
pressed up against the tiny heatsink on the TOP223Y's?

Yes, I noticed that, too. Hopefully, the TOP does not get all that
hot.

I doubt it would (for that heatsink) as it's got next to no radiative
qualities (being partially masked by the cap) and only a small thermal
mass. It might just be there to rest the cap on. ;-)

Cheers, T i m